The present invention relates to an improvement in the methods used to perform chevron osteotomy procedures that are commonly employed in bunion correction surgery. More specifically, to the design of a device that will aid orthopedic surgeons in making the precise bone cuts that are necessary for the successful completion of a biplane chevron osteotomy procedure and the treatment of a hallux valgus or bunion deformities.
A hallux valgus deformity is a very common foot disorder that results in the formation of a bunion on a patient""s foot which can be a source of pain and embarrassment. The deformity is a result of a static subluxation of the first metatarsalphalangeal joint (herein after referred to as the MTP joint) with a lateral deviation of the big toe and a medial deviation of the first metatarsal. More specifically, the word hallux is the medical term for the big toe and valgus is an anatomical term which refers to a deformity that is oriented in a direction away from the midline of the body. That is to say, the term hallux valgus describes a big toe that, from its tip to its base, is deformed in an outward manner in relation to the body of the foot. The condition can also be medically described in terms of the first metatarsal bone as metatarsus primus varus which refers to the orientation of the first metatarsal from its tip to its base being pointed towards the midline of the foot.
The result of this skeletal deformity is very often a large protruding bump on the outside base of the big toe that can be very sensitive to any pressure created by contact. Additionally, the condition is self-perpetuating in that the pressure it creates against the patient""s footwear causes the metatarsal bone at the point of contact to thicken. This thickening at the head of the metatarsal increases the size of the resulting bunion which adds to the pressure at the point of contact which in turn increases the severity of the condition and the associated discomfort to the patient.
The most common cause of a hallux valgus condition is the prolonged deformity of a foot which is most commonly associated with the long term wearing of improperly fitting footwear coupled with some sort of preexisting susceptibility resulting from such things as genetic factors or prior trauma. The footwear connection to the disorder is supported by the fact that it is much more common in women who are prone to wearing high heel shoes having a constricted forefoot area. This tends to force the big toe into an abnormal position which can cause the associated muscles to migrate laterally. Once this migration of the muscles passes outside of the line of the MTP joint the resulting hallux valgus condition tends to reenforce itself and continually worsen.
The first step taken in the medical diagnosis and treatment of a hallux valgus condition is to accurately define a number of critical measurements through the use of a series of X-rays taken of the foot""s bone structure. One of these is the intermetatarsal angle (herein after referred to as the IM angle) which is defined by the relationship of the first metatarsal shaft compared to the line of the second metatarsal shaft and generally in normal circumstances is between 6 and 9 degrees of deviation.
Another of the measurements taken is the determination of the hallux valgus angle (herein after referred to as the HV angle) which defines the angle of the line created at the MTP joint between the first metatarsal bone shaft and the first phalangeal bone shaft. This angle is generally considered to be within the normal range at 9 to 10 degrees and any HV angle that measures greater than 12 degrees is considered to be in the abnormal range requiring some sort of corrective action to be taken. Additionally, the distal metatarsal articular angle (herein after referred to as the DMAA) can also be measured which quantifies the angle created between the line if the first metatarsal shaft and the metatarsal head""s contact surface at the MTP joint.
Finally, the preliminary examination will also include an evaluation of the condition of the MTP joint to determine whether there has been a lateral subluxation of the joint. The combined evaluation of these and other factors will determine the course of action to be taken and in general terms a patient with a congruent MTP joint (a joint with no lateral subluxation), an IM angle of less than 15 degrees, and a HV angle of less than 30 degrees is a candidate for chevron osteotomy corrective surgery. For those patients who""s hallux valgus condition does not fall within these parameters there are other corrective procedures available.
The chevron osteotomy procedure for the correction of a hallux valgus condition has been around for a long time so it is quite natural that there exists numerous devices that are intended to aid a surgeon in the performance of a chevron osteotomy. An example of this type of device is illustrated in U.S. Pat. No. 5,843,085 issued to Graser 1998. The Graser patent describes a device which is intended to be used as a cutting guide in three different types of osteotomy procedures and consists of a two piece jig having multiple cutting slots and which may also require the use of more than one KIRSCHNER wire. While the device performs its desired functions, the fact that it is designed to perform multiple functions means that it is inherently complex and cumbersome to use which increases the risks of error when compared to a hypothetical design for a single use device.
Therefor, from the forgoing discussion it can be seen that it would be desirable to provide a device that would aid a surgeon in performing a biplane chevron osteotomy procedure for the correction of a hallux valgus condition. Additionally, that it would be advantageous to provide such a device that would be simple to use and that would allow the surgeon to make the complex bone cuts involved time after time with a high degree of accuracy.
It is the primary objective of the present invention to provide a means by which a surgeon can use a device that will aid him in making the V-shaped biplane cuts in the first metatarsal bone of a human foot that are necessary to perform a biplane chevron osteotomy procedure to correct a hallux valgus or bunion deformity.
It is an additional objective of the present invention to provide such a device that will allow a surgeon to precisely mark the forward end of the first metatarsal bone in such a manner that will provide a clear guide in making the subsequent primary superior and inferior osteotomy cuts through the stem of the first metatarsal.
It is an additional object of the present invention to provide such a device that will allow for the making of such cuts in the precise location on the metatarsal that is desired and also at the exact 67 degree angle, or formed so as to measure any other angle as desired in the procedure between the superior and inferior components of the primary osteotomy cut in the chevron procedure.
It is an additional objective of the present invention to provide such a device in which the initial marking portion (the primary guide body) is designed in such a way that the forward marking portion will slip into the primary superior and inferior cuts allowing the most forward surface of the secondary guide body to fit tightly against the distal surface of the capital fragment of the metatarsal.
It is a further objective of the present invention to provide such a device that has a secondary guide body formed in a such a manner so that its sides are precisely angled to provide the surgeon with guiding surfaces to aid in the making of the secondary superior and inferior cuts necessary to complete the bone cutting stages of the biplane chevron osteotomy.
It is a still further objective of the present invention to provide such a device to aid a surgeon in the performance of a biplane chevron osteotomy that can be easily manufactured in an inexpensive manner which will facilitate its wide distribution and thus improve the quality of the hallux valgus repair procedures taking place and therefor improve the quality of the patient""s life.
These objectives are accomplished by the use of a cutting jig apparatus used in biplane chevron osteotomy surgery for the correction of a hallux valgus (or bunion condition) in which the redirection of the joint between the first metatarsal and the first phalangeal bone is performed. The purpose of the chevron osteotomy is to remove a wedge of bone from the forward portion of the first metatarsal which allows these bones to be realigned in a manner that lessens or completely corrects the patient""s hallux valgus deformity.
In the past these cuts were typically made by hand in order that the wedge of bone be removed. The problem with this method is that the procedure requires that two cuts be made at precise angles in order for the remaining bone surfaces to match properly so that the osteotomy will heal adequately. While the first of these cuts is relatively easy to make, the second can be very difficult to make without a precise cutting guide. Therefore, the use of freehand techniques of the past led to problems in the length of time the surgical procedure took and often resulted in and errors made during the cutting process which could lead to healing problems.
The first step in the use of the present invention is to remove the medial eminence from the distal head of the first metatarsal. This procedure removes a significant portion of the protruding bone surface that created the problem and leaves a relatively flat surface to work with. Once this has been completed, a perpendicular KIRSCHNER wire (herein after referred to as a K-wire) is inserted into this surface at the center of the metatarsal head. The K-wire then provides a device which allows the present invention to be precisely positioned on the distal surface of the first metatarsal.
The positioning of the present invention is accomplished by slipping the body of the invention over the K-wire by the use of the K-wire hole that longitudinally spans the length of the secondary guide body of the invention. The use of the K-wire in this function serves two purposes. First, it places the invention in a perpendicular orientation to the surface of the metatarsal from which it can be rotated into the proper orientation for bone marking purposes and second, it serves to hold the invention in place during the metatarsal marking operation ensuring that the primary Chevron cuts will be made properly. It should also be stated that other means of holding the device may be possible.
With the V-shaped cutting edge of the present invention in the proper location, the upper surface of the invention is tapped with a hammer which forces the V-shaped cutting edge into the surface of the metatarsal bone leaving a V-shaped mark opening away from the metatarsal head. This mark is then used as a guide, after the removal of the present invention, by a surgeon for making the primary superior and inferior chevron cuts into the body of the metatarsal. After the completion of these cuts, the most forward portion (or the primary guide body) of the present invention is placed within the gap created by the cuts in a manner that places the forward surface of the secondary guide body against the surface of the metatarsal bone. This allows the surgeon to use the outer surfaces of the secondary guide body as guides to make the secondary superior and inferior chevron cuts at angles that will match up perfectly with surfaces of the primary cuts.
The completion of the secondary cuts separates a wedge of bone from the body of the first metatarsal and the present invention is removed from the cuts. The wedge of bone is then removed which leaves an open V-shaped chevron biplane cut having all of the inside cut edges matching perfectly which allows the stem and capital fragments of the first metatarsal to be inwardly realigned in relation to one another to close the gap created by the removal of the bone wedge. This realignment allows the capital fragment of the first metatarsal to be shifted laterally and oriented out of valgus, thus correcting the abnormal shape in the foot created by the long standing valgus drift due to increased DMAA and thereby alleviating the bunion condition. The stem and capital fragments of the first metatarsal are then generally held in place during the healing process by the use of a pin, screw, or other similar device and the healing of the bone will then allow the patient normal use of the foot.
For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention.